1. Field of the Invention
This invention relates to phase-locked loops. In particular, the invention relates to the charge pump in phase-locked loop circuits.
2. Description of Related Art
A phase-locked loop (PLL) circuit generates an output signal based on a control voltage representing the phase difference between a reference phase signal and a feedback signal. A charge pump circuit pumps current to be converted into the control voltage.
The charge pump circuit is normally biased by a charge pump bias circuit. The charge pump bias circuit provides a reference signal to establish the amount of current to be pumped. In traditional PLL circuits, the charge pump circuit continuously consumes power whether or not the PLL circuit is locked. Between pulses in the output signal, the charge pump circuit is idle, but still draws current, wasting power.
Therefore there is a need in the technology to provide a simple and efficient method to control a charge pump in phase-locked loop circuits.